F18 PASSIVE TRANSFER OF IgG FROM HORSES WITH ALOPECIA AREATA-LIKE HAIR LOSS

¹Gardner SH, ²Olivry T, ¹Lindsey NJ and ¹Tobin DJ. ¹Dept. of Biomedical Sciences, University of Bradford, West Yorkshire, England. ²College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.

Alopecia areata (AA) is a presumptive autoimmune hair loss disorder affecting humans and several other mammalian species. Recently we have demonstrated the presence of anti-hair follicle (HF) auto-antibodies in humans, horses and dogs with AA as well as in the C3H/HeJ AA mouse model. However, it is unclear whether these antibodies are pathogenic; some suggest they result secondary to follicular damage. Previously, we reported limited telogen arrest and shedding in murine skin after passive transfer of equine AA whole serum and now extend this investigation by passively transferring purified equine AA IgG into murine haired skin. Sera used for this study were selected on the basis of high titer anti-HF antibodies by indirect immunofluorescence and western blotting and were re-tested after IgG purification. Anagen III/IV C57Bl/10 murine skin was injected intradermally with 5mg IgG twice weekly for 44 days. Thereafter, dorsum skin was harvested at both 7 hours and 10 days post final injection for H&E staining. Full hair regrowth was observed around the injection site in all mice by 12 days post first injection. However, the injection site itself remained hairless for a further 14 days in mice treated with normal IgG but did not regrow until 37 days later in mice treated with AA IgG. H&E stained sections of AA IgG-treated peri-injection site skin revealed a spatially-restricted loss of hair follicles associated with the massive mixed-cell inflammatory infiltrate located around the hair follicles and in the dermis. Other notable findings included epidermal thickening and cyst formation. None of these features was observed in normal IgG-treated skin. While this study suggests that AA IgG injected into murine haired-skin can have local negative effects on hair growth consistent with an inflammatory response, a pathogenic role for anti-hair follicle antibodies in AA awaits confirmation.